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Abstract:

A wind energy plant comprising a rotor having blades and a generator
driven by said rotor for generating electric energy. The pitch of the
blades can be adjusted and a pitch system for adjusting the pitch angle
of the blades is provided, which is supplied by a hub power source. An
additional electric load is provided on the hub. A pitch power control
device is provided which dynamically distributes the power of the hub
power source between the pitch system and the additional electric load
and further acts on the pitch system such that the power consumption
thereof during high-load operation is reduced. Thus, the power
consumption of the pitch system during high-load operation can be reduced
and additional power provided for operating the additional load. Even
high-performance additional loads, such as a blade heater, can be
operated in this way, without having to boost the hub power source.

Claims:

1. A wind energy installation comprising a rotor comprising a hub and
blades adjustable in terms of pitch, a generator driven by the rotor for
generating electrical energy, a pitch system for adjusting the pitch
angle of the blades, a hub power source for feeding the pitch system, a
supplementary electrical load is provided on the hub, and a pitch power
controller configured to dynamically distribute the power from the hub
power source between the pitch system and the supplementary electrical
load and to act on the pitch system such that the power draw by the pitch
system is reduced in a high-load mode.

2. The wind energy installation as claimed in claim 1, comprising an
adaptation device configured to monitor operating conditions for the
pitch system or for the supplementary electrical load and to act on the
pitch power controller.

3. The wind energy installation as claimed in claim 2, wherein the
adaptation device comprises a current surveillance module configured to
monitor the flow of current on the pitch system and to modify operating
parameters for the pitch system when a limit value is reached.

4. The wind energy installation as claimed in claim 3, wherein the
current surveillance module comprises a load sensor.

5. The wind energy installation as claimed in one of claims 2 to 4,
wherein the adaptation device comprises a restrictor module for the pitch
control system.

6. The wind energy installation as claimed in claim 5, wherein the
restrictor module is configured to target values for the pitch control by
determining a restrictor operating point with reduced target values for
speed or power at an operating point.

7. The wind power installation as claimed in claim 5, wherein the
restrictor module is configured to reduce the regulatory quality of the
pitch control.

8. The wind energy installation as claimed in claim 2, wherein the
adaptation device comprises an interruption module configured to act on
the pitch power controller such that the high-load mode is terminated
when predetermined states of the wind energy installation occur.

9. The wind energy installation as claimed in claim 1, comprising an
enabling device configured to be actuated by the pitch system and to
prompt the pitch power controller to change over to the high-load mode.

10. The wind energy installation as claimed in claim 9, wherein the
operating control system of the wind energy installation is connected to
an input of the enabling device by a request signal line.

11. A method for operating a wind energy installation comprising a rotor
comprising a hub and blades adjustable in terms of pitch, a generator
driven by the rotor for generating electrical energy, a pitch system for
adjusting the pitch angle of the blades, a hub power source for feeding
the pitch system, and a supplementary electrical load, the method
comprising operating the supplementary electrical load in a high-load
mode, feeding in the high-load mode the supplementary electrical load
from the hub power source and reducing in the high-load mode the power
drawn from the hub power source by the pitch system.

12. The method as claimed in claim 11, comprising monitoring operating
conditions for the pitch system or for the supplementary electrical load
and acting on the pitch power controller.

13. The method as claimed in claim 12, comprising monitoring the flow of
current on the pitch system and modifying operating parameters for the
pitch system when a limit value is reached.

14. The method as claimed in claim 13, comprising targeting values for
the pitch control by determining a restrictor operating point with
reduced target values for speed or power at an operating point.

15. The method as claimed in claim 14, comprising reducing the regulatory
quality of the pitch control.

16. The method as claimed in claim 11, comprising acting on the pitch
power controller such that the high-load mode is terminated when
predetermined states of the wind energy installation occur.

Description:

REFERENCE TO RELATED APPLICATIONS

[0001] This application is a national stage application under 35 USC 371
of International Application No. PCT/EP2011/050831, filed Jan. 21, 2011,
which claims the priority of German Application No. 10 2010 005 286.8,
filed Jan. 21, 2010, the entire contents of which are incorporated herein
by reference.

FIELD OF THE INVENTION

[0002] The invention relates to a wind energy installation having a rotor
for driving a generator, wherein the rotor has blades which are both
adjustable in terms of pitch and heatable by blade heating.

BACKGROUND OF THE INVENTION

[0003] Wind energy installations are suitable as local generators of
electrical energy, particularly also for use in thinly populated areas
with favorable wind conditions. Many of these thinly populated areas are
in zones with an adverse climate. These also include areas with a cold
climate, in particular. In order to toughen up wind energy installations
for operation under "cold climate" conditions, blade heating is usually
necessary for the rotor blades. This is because it has been found that,
without such heating, ice forms or collects on the rotor blades during
operation, said ice having disadvantageous effects in multiple respects.
Firstly, it alters the aerodynamic profile of the rotor blades, which
usually results in significant impairment precisely when the rotor blades
have a very advanced aerodynamic design. Furthermore, the formation of
ice increases the weight of the rotor blade, which increases the forces
to be absorbed by the suspension of the rotor blades; this applies
particularly during operation at relatively high speeds and
correspondingly growing centrifugal forces or when there are imbalances
in the hub as a whole which are caused by different ice formation on the
respective rotor blades. Finally, there is also a not inconsiderable risk
to persons and objects in the vicinity of the wind energy installation as
a result of ice being cast, i.e. as a result of pieces of ice becoming
detached from rotor blades and being flung away. In general, the wind
energy installation is shut down when there is ice formation on the rotor
blades. In order to avoid these disadvantages, blade heating may be
provided. On account of the size of the rotor blades and sometimes harsh
climatic conditions, however, a relatively large amount of heating power
is required for the blade heating. Providing said heating at the location
at which it is needed, namely in the hub of the rotor, requires some
additional complexity, resulting in additional cost.

[0004] In order to be able to still supply power to a large electrical
load, such as a blade heater, without amplifying the power available in
the hub, a design has become known in which the wind energy installation
is shut down while the rotor blades are being heated (DE 103 23 785 A1).
Although this has the disadvantage that no further electrical power is
generated by the wind energy installation during the phases in which the
rotor blades are being heated, this has the advantage that barely any
power needs to be expended for the individual requirements of the wind
energy installation during the shutdown, and hence all of the electrical
power available in the hub can be used for heating the rotor blades.
Usually, heating takes place over a period of up to 15 minutes, and after
that the wind energy installation is started up again. Although heating
using a stopping device of this type has proven itself in principle, this
still has the disadvantage that no electrical energy is generated during
the heating time, that is to say that the yield is reduced.

[0005] This is made even worse by the fact that restarting afterwards is
extremely time consuming, which further reduces the production of energy
by the wind energy installation. Above all, however, a serious
disadvantage is that the ice formation per se is not prevented and hence
a risk to the surroundings cannot be ruled out.

SUMMARY OF THE INVENTION

[0006] The invention is therefore based on the object of improving wind
energy installations of the type cited at the outset such that large
loads, such as a blade heating apparatus, can also be operated on the hub
and at the same time complex amplification of the supply of power is
avoided.

[0007] The solution according to the invention lies in the features as
broadly described herein. Advantageous developments are the subject
matter of the detailed embodiments described below.

[0008] In a wind energy installation comprising a rotor having blades and
a generator, which is driven by the latter, for generating electrical
energy, wherein the blades are adjustable in terms of pitch and a pitch
system for adjusting the pitch angle of the blades is provided which is
fed from a hub power source, the invention provides a pitch power
controller which dynamically distributes the power provided by the hub
power source between the pitch system and the supplementary electrical
load and in addition acts on the pitch system such that the power draw by
the latter is reduced in the high-load mode.

[0009] A few terms which are used will first of all be explained below:

[0010] A supplementary electrical load is understood to mean a device
which is arranged on the rotor hub and provides additional functionality
which is not required for basic operation of the wind energy
installation. In particular, this includes large loads which each
independently have a power draw which is at least one fifth, preferably
half, of the electrical power available in the hub. Examples of such
supplementary loads are blade heating devices for the rotor blades,
particularly with resistance heating or fan heaters, air-conditioning
appliances for dehumidifying the hub, cooling appliances for hot-climate
versions, powerful warning and protective devices, such as high-intensity
hazard lighting for the rotor blades, or particularly complex
measured-value capture systems, such as LIDAR or phased-array radar
systems for wind or turbulence recognition and determination.

[0011] A high-load mode is understood to mean that the wind energy
installation is set up such that the supplementary electrical load is
supplied with power as a matter of priority. The difference over the
normal mode is thus that in the normal mode the priority is given to
speed regulation for the wind energy installation, which allows optimum
energy yield, and the supplementary electrical load is not operated or is
operated only to a small extent.

[0012] Dynamically distributed is understood to mean that the power
transmitted from the pitch power controller to the pitch system or the
supplementary electrical load is variable during operation. In
particular, dynamically distributed may also mean that the pitch power
controller regulates the power requirement of the supplementary
electrical load. Dynamic distribution can therefore also be effected by
switching on or switching off or by setting the operating point of the
electrical loads.

[0013] A hub power source is understood to mean a limited-capacity source
for electrical energy which provides electrical power in the rotor
assembly. Usually, this will be a power-limiting transmission system of
the wind energy installation on which the rotor is arranged so as to be
able to rotate. By way of example, this transmission system may be a
slipring, and in this case the hub power source is limited by the maximum
power which can be transmitted by the slipring. Alternatively, the hub
power source can also generate the electrical power autonomously, for
example using a storage battery and/or a shaft generator.

[0014] The invention is based on the idea of splitting the electrical
power provided by the hub power source in the rotor differently in the
high-load mode than in the normal mode, namely such that the electrical
power drawn by the pitch system is reduced and hence kept within limits
which are such that a large portion of the electrical power can be
provided for operating the supplementary electrical load. The
supplementary electrical load can thus be operated at full power without
restrictions. In the case of a blade heater, this means the full heating
effect, as has conventionally been able to be achieved only when the wind
energy installation has been shut down. In essence, the invention thus
provides for dynamically modified power branching, with the power draw by
the pitch system being reduced in the high-load mode and hence additional
power being provided for operating the supplementary electrical load.
Amplification of the hub power source or substantial operating
restrictions as in the prior art can thus be avoided. By virtue of the
invention, the conventional hub power source which is already present is
thus sufficient despite the substantial power requirement for the
supplementary electrical load. No additional complexity for amplifying
the hub power source is required.

[0015] Preferably, the pitch power controller is designed such that the
power is limited not rigidly but rather adaptively. To this end, an
adaptation device is expediently provided which monitors the pitch power
controller and acts on it. The adaptation device may be of various
design. Thus, in a first version, the adaptation device may have a
current surveillance module. In this case, the power drawn by the pitch
system is reduced when the hub power source is loaded to an adjustable
maximum degree (for example 90%). This ensures that even with a high
level of activity there is always sufficient power available for the
supplementary electrical load. Preferably, this comprises a load sensor.
This may be produced on the pitch drive, for example as a current sensor
(direct measurement), or the power draw can be determined from signals
for pitch adjustment rate and acceleration (indirect measurement); if it
turns out that the pitch system is under a high load in this case,
appropriate action is taken to reduce the power draw. Preferably, the
current surveillance module is designed to act on parameters of the pitch
system, for example to reduce the gain of a regulator or the maximum
permissible pitch adjustment rate in the pitch controller.

[0016] In addition, provision may be made for the adaptation device to
have a restrictor module. This determines an appropriate restricted
operating point for the respective operating point of the wind energy
installation, at which restricted operating point the speed and power
generated by the generator are reduced. This increases the reserve up
until the respective limit values (speed and power) have been reached, so
that subsequently there is significantly less pitch activity required by
utilizing this reserve.

[0017] Expediently, the restrictor module is also designed to reduce the
regulatory quality of the pitch control system. This expands tolerance
bands and consequently reduces the activity of the pitch system, as a
result of which there is ultimately more power available for the
supplementary electrical load from the hub power source.

[0018] For protection purposes, the adaptation device may also be provided
with an interruption module. This is designed to output a suspend signal
to the pitch power controller, and hence to disable the high-load mode,
when predetermined states of the wind energy installation occur.
Preferably, the interruption module is connected to a device for
recognizing a voltage dip. Hence, in the event of a system disturbance
during a voltage dip, the wind energy installation is able to interrupt
the high-load mode, and hence to make all of its resources available for
handling the voltage dip. Furthermore, a device for recognizing a system
return may be provided. However, in the event of the system returning,
startup of the wind energy installation and the alterations in the pitch
which are required for this have priority, as a result of which the
supplementary electrical load is expediently disconnected for this. The
interruption module may have further signal inputs for particular
high-load states of the pitch system, particularly for the reaching of
maximum current in the pitch system or the implementation of emergency
running.

[0019] The invention also extends to a method according to the independent
claim. For more detailed explanation, reference is made to the
description above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The invention is explained below using an exemplary embodiment with
reference to the appended drawing, in which:

[0021] FIG. 1: shows an overview illustration of a wind energy
installation based on an exemplary embodiment of the invention;

[0022]FIG. 2: shows a schematic illustration of the electrical components
in the hub of the wind energy installation shown in FIG. 1; and

[0024] A wind energy installation based on an exemplary embodiment of the
invention comprises a gondola 11 arranged on a tower 10 so as to be able
to pivot in azimuthal direction. The front of said gondola has a rotor 2
arranged on it so as to be able to rotate, which drives a generator 13
via a generator shaft 12 in order to generate electrical energy. In the
exemplary embodiment shown, the generator 13 is in the form of a dual-fed
asynchronous generator and is interconnected with a converter 14. The
electrical power provided by the generator 13 and the converter 14 is
routed via a power cable 15, running in the tower 10, to the base of the
tower, where it is connected to a machine transformer 16 for the purpose
of outputting the generated electrical energy at a medium voltage level.

[0025] In addition, the gondola 11 contains an operating control system
17. This is designed to actuate the individual systems of the wind energy
installation, and it is furthermore connected for communication purposes,
for example via a radio interface 18, to superordinate control devices,
such as a farm master on a wind farm and/or system control centers
belonging to a power supply system operator.

[0026] The rotor 2 comprises a plurality of rotor blades 21 which are
arranged so as to be adjustable in terms of their pitch angle θ on
a hub 20 at the end of the generator shaft 12. For the purpose of
adjusting the pitch angle θ, a pitch system 4 is provided which
comprises an annular gear 41 which is arranged at the blade root of the
respective rotor blade 21 and with which a drive sprocket on a server
motor 42 arranged firmly on the hub engages. For the purpose of actuating
the pitch system 4, a dedicated pitch control system 43 may be provided
in the hub. The pitch control system 43 receives guidance signals from
the operating control system 17. In addition, the hub 20 contains a hub
power source 40 for the pitch system 4. The hub power source 40 may be a
slipring, in particular, by means of which electrical power is routed
from the gondola 11 into the hub 20. However, it may alternatively or
additionally also be a battery 40' or a shaft generator 40'' running on
the shaft 12. The way in which the pitch system 4 works is such that a
target value is prescribed for the pitch angle θs by the
operating control system 17, and said target value is then adjusted by
the pitch control system 43, by operating the drive motor 42 which acts
on the annular gear 41 of the rotor blades 21, by rotating the rotor
blades 21 until the correct pitch angle θ has been reached.

[0027] The rotor blades 21 are also provided with a blade heater 5, which
is preferably arranged at least in the region of a nose strip of the
rotor blades 21. In the exemplary embodiment shown, the blade heater 5 is
in the form of an electric heating element. It is a supplementary
electrical load in the hub 20, which supplementary electrical load
requires considerable electrical power in the heating mode ("high-load
mode"). Energy is supplied by using said hub power source 40, which also
supplies power to the pitch system 4. In order to split the power between
the pitch system 4 on the one hand the blade heater 5 on the other, the
invention provides a pitch power controller 6. This has a control block
60 and a switching block 61 having a power input and two power outputs.
The power input has the hub power source 40 connected to it. One of the
two outputs has the pitch system 4 connected to it, and the other of the
two outputs has the blade heater 5 connected to it. The pitch power
controller may be designed for digital changeover, which involves only
one of the two systems being supplied with power at a time; in the
exemplary embodiment shown, however, it is meant to be a system which can
split the power, so that both systems can also be supplied with power
simultaneously (albeit not necessarily with power of the same magnitude).

[0028] The switching block 61 of the pitch power controller 6 is operated
by a control block 60. This is designed to reduce the power drawn by the
pitch system 4 in a heating mode. To this end, the control block 60 is
connected to the pitch control system 43 by means of a first signal line
62. The effect achieved by this is that the power draw by the pitch
system 4 is reduced, and there is thus always sufficient power available
for the blade heater 5 for the heating mode.

[0029] The pitch power controller 6 has an adaptation device 8 interacting
with it. This has a plurality of functional modules, namely a current
surveillance module 81, a restrictor module 82 and an interruption module
83. The current surveillance module 81 is designed to monitor the
operation of the pitch system 4 by means of a power sensor 44 in the
heating mode. If the pitch system is operated such that a critical value
for the power draw is reached (for example if, together with the blade
heater, 90% of the power of the hub power source 40 were demanded), the
hub power source 40 is protected from overload by influencing regulator
parameters of the pitch system control system 43. In particular,
limitation of the adjustment rate and acceleration for the pitch drive 42
can be prompted by this means.

[0030] The restrictor module 82 is designed to operate the wind energy
installation at relatively low load as a preventive measure. To this end,
on the basis of the normal operating point which is obtained for the
respective ambient conditions, particularly in relation to the parameter
speed and power, offset values are formed which are deducted from the
values for the normal operating point so as thereby to produce modified
target values for the parameters at a modified operating point. To this
end, an interface 84 is provided which applies the altered data for the
operating point to the operating control system 17.

[0031] Specifically, this means that, for example on the basis of an
operating point with a speed nB of 20 revs/min, in a partial-load
operating situation the target speed for the heating mode a modified
operating point with a lowered speed nB' of 16 revs/min is
determined, with the tolerance limits and the action threshold of the
pitch system control system 43 not following accordingly, however. There
is therefore a substantial buffer, which means that even in the event of
incident winds which are suddenly stronger, it is not necessary for the
pitch system 4 to be operated, as a result of which the power provided by
the hub power source 40 can be used almost to the full extent for the
blade heater 5. A similar situation applies to the full-load operating
situation. In this case, instead of the speed, the operating point for
the power would be lowered accordingly, which results in an appropriate
power reserve which in turn reduces the probability of the pitch system 4
being switched on accordingly.

[0032] The interruption module 83 has a plurality of signal inputs, which
are each designed to detect particular states. Thus, a first signal input
has a detector 85 for a voltage dip arranged at it. It should be noted
that the detector 85 may be a standalone component or a connection to
another device, which is already present anyway and performs voltage dip
detection (for example in the operating control system 17). When the
occurrence of a voltage dip is detected in this manner, the interruption
module 83 acts on the pitch power controller 6 such that the power which
the hub power source 40 provides for the blade heater 5 is severely
reduced or even switched off completely. The effect achieved by this is
that in such an extra ordinary operating situation the pitch system 4 is
supplied with power to a sufficient degree to be able to make even large
pitch changes at a high pitch adjustment rate and acceleration.
Accordingly, a detector 86 for system return, a detector 87 for pitch
emergency running and in addition a sensor 89 for recognizing when the
maximum flow of current from the hub power source 40 has been reached are
provided. In addition, an overspeed detector 88 is connected, so that
when a limit speed is reached the suspend signal is output by the
interruption module 83. If this furthermore involves a limit value for a
speed acceleration being exceeded, a rotor brake 22 is operated.

[0033] In addition, an enabling device 18 may be provided which is
operated by the pitch system 4. Said enabling device comprises two
inputs, one connection for an enabling signal which is output by the
pitch system 4 and one connection for a request signal for the
supplementary electrical load, which is output by the operating control
system 17. An output of the enabling device 80 is connected to the pitch
power controller. The enabling device 80 interacts with the pitch power
controller 6 such that in the event of predetermined installation states
of the supplementary electrical loads occurring the heating system 5 is
switched on and changed to the heating mode. This can be brought about
directly by the signal applied to the enabling device 80 by the pitch
system 4, as a result of which the pitch power controller 6 assigns the
power to the heating system 5. Alternatively, a two-stage enabling system
may be provided, with the operating control system 17 applying a request
signal for the heating mode to the enabling device 80, which request
signal is connected to the pitch power controller only if the enabling
signal from the pitch control system 4 is also present. Examples of such
operating states are, in particular, installation operation of partial
load, when the pitch system 4 is in a kind of sleep mode, installation
operation for regular wind with only minor pitch activities, or else
installation shutdown.

[0034] An example of a mode of action is shown in FIG. 3. FIG. 3a shows
various phases with or without heating mode switched on. In phase I, the
heating mode has not yet been switched on, i.e. the wind energy
installation is being operated in the normal mode. In the subsequent
phase II, the heating mode is activated. FIG. 3b shows the speed values
which have been adjusted by the pitch system 4. FIG. 3c shows the
activity of the pitch system 4 in the form of operation of the pitch
actuating drive 42 for adjusting a pitch angle Θ, with which the
speed prescribed by the operating point as shown in FIG. 3b is achieved.
It can be seen that compliance with the speed preset in phase I requires
brisk activity by the pitch system. At the time t1, the restrictor
module 82 determines a modified operating point with a relatively low
speed nB'. The pitch power controller 6 is activated and assigns a
large portion of the power to the blade heater 5. In addition, the
current surveillance module 81 is operated. The effect can be seen in
FIGS. 3b and c, where the speed discrepancies are greater in phase II
than in the preceding operating phase I without heating mode, but these
discrepancies are noncritical on account of the preemptive speed lowering
and do not exceed the speed nB of the previously set operating
point; the mode is therefore safe. Since greater discrepancies can
therefore be permitted, the activity of the pitch system 4 in phase II is
reduced. This can easily be seen in FIG. 3c. Since the actuating
amplitudes and the rate and also acceleration are reduced, the current
draw by the pitch system 4 is correspondingly lower, which means that
there is sufficient power available for operation of the blade heater 5.

[0035] This state continues until a short occurs in the system in phase
IIb. This short is recognized by the detector 85 and is applied as a
signal to the interruption module 83. The interruption module then
disables the heating mode by actuating the pitch power controller 6 such
that the power is provided only for the pitch system 4. The power for the
blade heater 5 is therefore removed. Accordingly, the modified operating
point and the restriction in respect of the activity of the pitch system
are also removed, which means that the wind energy installation can react
to this fault situation to the full extent. This phase IIb continues
until the system return is recognized by means of the detector 86. The
return to the heating mode then occurs in phase IIc, said heating mode
being executed in accordance with phase IIa.

[0036] It can also be assumed that an overspeed in the rotor 2 occurs (for
example on account of an undervoltage in the system to which the
transformer 16 is connected). The speed exceeds the upper speed limit
nH at the time t4 with a keenly rising tendency (i.e. large speed
acceleration). This is recognized by the overspeed detector 88, and the
interruption module 83 operates the pitch power controller 6 such that
the power is provided only for the pitch system 4, as a result of which
said pitch system can react to the overspeed with the full activity. In
order to completely rule out a risk to the safety of the wind energy
installation resulting from the high speed acceleration, the rotor brake
22 is additionally operated in order to stabilize the speed (phase IId).